1. Field of the Invention
The present invention relates to a supporting apparatus for a medical instrument, which is capable of maintaining the supported medical instrument at a desired position.
2. Description of the Related Art
For example, Jpn. Pat. Appln. KOKOKU Publication No. 63-36481 and Jpn. Pat. Appln. KOKAI Publication No. 7-143995 disclose a supporting apparatus for a medical instrument. The medical instrument supporting apparatus disclosed in these publications supports a medical instrument, such as an endoscope or a surgical microscope, on an end of an arm of the apparatus, smoothly moves it to a desired position and maintains it at the position. The conventional medical instrument supporting apparatus is of a counterbalance system, in which a counterweight is located on the other end of the arm beyond a fulcrum to keep the balance with the medical instrument.
In this system, for example, one of four link members forming a parallelogram link is rotatably attached to a support column. A support arm which holds a surgical microscope is located at one end of the link member attached to the support column, and a counterweight is located on the other end of the link member beyond the support column. The counterweight is moved horizontally and vertically in association with horizontal and vertical movements of the support arm. Thus, the balance between the surgical microscope and the counterweight is kept to carry out delicate surgical operations.
Jpn. Pat. Appln. KOKAI Publication No. 7-227398 and Jpn. Pat. Appln. KOKAI Publication No. 2001-258903 discloses a supporting apparatus, which adjusts the balance between an endoscope and a counterweight via a similar parallelogram link to smoothly and exactly move the endoscope to observe a subject part in the abdominal cavity and fix it at a required position.
In the conventional supporting apparatuses for medical instruments as described above, the counterweight is moved in association with the movement of the medical instrument, such as an endoscope or a surgical microscope. For example, if the medical instrument is projected horizontally in one direction, the counterweight must be projected in the opposite direction. In an operation room, a number of various apparatuses are placed and a number of assistants or nurses are required to do their works in a limited space where a patient lies. Therefore, if the counterweight projects in the direction opposite from the medical instrument, it may be brought into contact with another apparatus or obstruct works of the nurses or the like. Further, if the movement of the counterweight is limited, it will be difficult to obtain a satisfactory field of view of the operator.